title: Effect of object location on the density measurement in cone-beam computed tomography versus multislice computed tomography.
abstract: BACKGROUND
  Bone density measurement in a radiographic view is a valuable method for evaluating the density of bone quality before performing some dental procedures such as, dental implant placements. It seems that Cone-Beam Computed Tomography (CBCT) can be used as a diagnostic tool for evaluating the density of the bone, prior to any treatment, as the reported radiation dose in this method is minimal. The aim of this study is to investigate the effect of object location on the density measurement in CBCT versus Multislice computed tomography (CT).
  
  
  METHODS
  In an experimental study, three samples with similar dimensions, but different compositions, different densities (Polyethylene, Polyamide, Polyvinyl Chloride), and three bone pieces of different parts of the mandibular bone were imaged in three different positions by CBCT and Multislice CT sets. The average density value was computed for each sample in each position. Then the data obtained from each CBCT was converted to a Hounsfield unit and evaluated using a single variable T analysis. A P value <0.05 was considered to be significant.
  
  
  RESULTS
  The density in a Multislice CT is stable in the form of a Hounsfield Number, but this density is variable in the images acquired through CBCT, and the change in the position results in significant changes in the density. In this study, a statistically significant difference (P value = 0.000) has been observed for the position of the sample and its density in CBCT in comparison to Multislice CT.
  
  
  CONCLUSIONS
  Density values in CBCT are not real because they are affected by the position of the object in the machine.
authors.affiliation: Department of Oral and Maxillofacial Radiology, School of Dentistry, Hamedan University of Medical Science, Hamedan, Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Eskandarloo
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Abdinian
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Salemi
authors.forename: Zahra
authors.initials: Z
authors.lastname: Hashemzadeh
authors.forename: Mehran
authors.initials: M
authors.lastname: Safaei
keywords: Bone density; cone-beam computed tomography; implant